Mstislav Rostropovich has put together a Fourth of July celebration in music, with freedom as its keynote, for the National Symphony Orchestra's second concert on the West Lawn of the Capitol. After its successful launching on Memorial Day, when Aaron Copland conducted the orchestra, the series finds Rostropovich at the head of the NSO supplemented by a large male chorus in Randall Thompson's "Testament of FREEDOM."

The 8 p.m. program will open with three European works that focus on the freedom theme, the first of them Beethoven's Egmont Overture.

Goethe's "Egmont," the play for which Beethoven provided incidental music, is set in the Netherlands during that country's long struggle against Spanish rule. King Philip II of Spain is in the background of the play in which the cruelty of the infamous Duke of Alba plays a major part. There is a scene between William of Orange and the people's hero, Egmont. The clue to the desire for freedom that dominates Beethoven's overture can be found in Egmont's final soliloquy, delivered just before his execution. He says, in parts, "I too will step out of this dungeon towards an honorable death; I die for the freedom for which I have lived and fought, and to which I now offer myself up as a willing victim."

Jan Sibelius wrote Finlandia in 1899, creating what has become one of the most famous of all works to proclaim in music a people's longing for freedom. In its original form, the tone poem is the finale of a suite called "Finland Awake," which Sibelius wrote for a pageant protesting the Russian rule of his country. So powerful was its impact that it was officially banned, and went unheard after the premiere until 1905. From that time, however, it has grown in fame and popularity throughout much of the world. It stands today as Findland's chief artistic expression of national pride.

It was similar stimulus that had led Antonin Dvorak a decade and a half earlier to write his Hussite Overture, called "Husitska." In that year, the director of the National Theater in Prague wrote a dramatic trilogy based on Hussite history, for which he asked Dvorak to provide the overture.

Again the political oppressor involved was czarist Russia, and, like Sibelius, Devorak had strong nationalist feelings which he set out with great vigor in the new overture. The work comes to a massive close as Dvorak combines the melody of a 15th-century Hussite chorale, "Ye warriors of god," with one of the most popular chorales of today's Czech people, the 13th-cen-

The balance of the Rostropovich program comes from three great American composers: Charles Ives, Randall Thompson and John Philip Sousa.

The Ives for next Wednesday night is an inevitable choice for that day, his Fourth of July. One movement of his "Holidays" Symphony, it is a treasure of national feeling for our birthday celebration. Ives himself wrote this description of the astounding piece:

"Near Redding Center, Conn, is a small park preserved as a Revolutionary Memorial. . . . Once upon a '4th of July,' some time ago, a child went there on a picnic, held under the auspices of the First Church and the Village Cornet Band. Wandering away from the rest of the children past the camp ground into the woods, he rests on the hillside of laurel and hickories, the tunes of the band and the songs of the children grow fainter and fainter; when -- 'mirabile dictu' -- over the trees on the crest of the hill he sees a tall woman standing.

"She reminds him of a picture he has of the Goddess of Liberty, but the face is sorrowful; she is pleading with the soldiers not to forget their 'cause' and the great sacrifices they have made for it. But they march out of camp with fife and drum to a popular tune of the day. Suddenly a new national note is heard. [Gen. Israel] Putnam is coming over the hills from the center; the soldiers turn back and cheer. The little boy awakes, he hears the children's songs and runs down past the monument to 'listen to the band' and join in the games and dances."

Ives added, "I put in as many feelings and rhythms as I wanted to put together. . . . I worked out combinations of tones and rhythms very carefully by kind of prescriptions, in the way a chemical compound that explosions would be made. . . ."

A year or so after he finished the Fourth of July, Ives and his insurance partner, Julian Myrick, were moving their offices. Myrick tells this amazing story: "We had a little safe, and he [Ives] had one part and I had another -- and he'd cleaned out his part, and I went to clean out my part -- and there's a stack of music. And I said, 'Charlie, you want me to throw this away?' And he came over -- he said, 'Why Mike! God, that's the best thing I've written!' -- and it was the Fourth of July, about to be thrown away!" Ives dedicated the work to Myrick.

No more appropriate climax could bring Wednesday's program to a rousing finale than "The Testament of Freedom," by Randall Thompson. Its words are by Thomas Jefferson, who wrote them partly in the years immediately before the outbreak of the Revolutionary War, and in part 40 years after that war was ended.

Thompson, who celebrated his 80th birthday April 21, wrote the "Testament" for men's voices and orchestra to mark the 200th anniversary of Jefferson's birth, an event observed in 1943. The principal sentiment of the work is heard in the lines that open and close it, taken from a paper Jefferson delivered to the Virginia Convention in 1974. They read: "The God who gave us life gave us liberty at the same time; the hand of force may destroy but cannot disjoin them."

Whether announced as a part of the program, or played in response to a demand for an encore, nothing could more strongly follow the Thompson than Sousa's greatest march, "The Stars and Stripes Forever." When its final chords end, the fireworks at the Washington Monument, where the Marine Band will have been playing a concert at the same time as the National Symphony's, will begin. From one end of the Mall to the other, Wednesday night is going to be an unprecedented musical Fourth. And all of it free, thanks to the Congress of the United States.